The invention relates to a display device for watches, for example wristwatches or pocket watches.
There are wristwatches having a 24-hour display, the dial thereof being provided with an hour display window displaying one of 24 hour numbers for one hour each, said hour numbers being provided on an hour disc arranged underneath the dial and so as to be rotatable relative to the hours display window. As the hour disc has to accommodate 24 hour numbers, with the hour numbers 20 and 24 taking up particularly much space due to their 2 at the beginning, the display window and the particular hour number visible therein have to be relatively small especially in case of wristwatches of smaller dimensions, thus aggravating the readability thereof. Representations of such a wristwatch can be found in the following special publications: Uhrenmagazin 7/8 96, Jun. 26, 1996, page 39; Armbanduhren 2 96, Jun. 5, 1996; and Chronos 4 96, Jun. 21, 1996.
In addition thereto there are wristwatches having two semicircular arcs arranged on a watch dial concentrically with respect to each other and radially spaced apart, each being provided with twelve hour numbers, one of the two semicircular arcs indicating 12 day hours and the other semicircular arc indicating 12 night hours. These two semicircular arcs have a two-arm hour hand associated therewith which carries out one revolution every 24 hours and the axis of rotation of which is concentric with the two semicircular arcs and the two arms of which are of different lengths, such that during one half of a 24-hour period the longer hand arm points to the hour numbers of the outer one of the two semicircular arcs and during the other half of a 24-hour period the shorter hand arm points to the hour numbers of the inner one of the two semicircular arcs. The two semicircular arcs take considerable space of the watch dial surface which sometimes may be undesirable for reasons of design or in case of watches the dial of which, in addition to various time displays, such as hour, minute and second displays, is to accommodate still further kinds of display, such as a date display and/or a moon phase display. Representations of such a wristwatch are contained in ARMBANDUHREN 3/97, page 42, and in Uhren Magazin 4/96, page 105.
The present invention is to overcome such disadvantages. In particular, a display device for watches is to be provided having a 24-hour display, which with little consumption of space on the wrist dial surface, renders possible good readability of the particular hour.
This is achieved by a display device for watches according to the invention, comprising a watch dial provided with a day hours display window for respectively displaying one of the hours of the day during daytime and a separate night hours display window for respectively displaying one of the hours of the night during nighttime, a day hours disc provided with twelve hour numbers and adapted to be rotationally advanced at hourly intervals such that a respective one of the day hour numbers is visible in the day hours window for one hour each during the hours of the day, and a night hours disc provided with twelve hour numbers and adapted to be rotationally advanced at hourly intervals such that a respective one of the night hour numbers is visible in the night hours window for one hour each during the hours of the night, wherein the two hour discs are at the most partly overlapping and the two hour display windows and the two hour discs are arranged such that the hour numbers of the day hours disc are visible only in the day hours display window and the hour numbers of the night hours disc are visible only in the night hours display window.
By using two separate hour discs and two separate hour display windows for the day hours display and the night hours display, respectively, there are possible on the one hand larger hour number representations than in case of one single hour display window and one single 24-hour disc. On the other hand, by using two separate hour discs and two separate hour display windows, it is sufficient to have the hour numbers 1 to 12 for each hour disc. Thus, a maximum of three two-digit numbers has to be accommodated for each hour disc, which may be reduced further to two two-digit numbers if the number 10 is written as Roman numeral X. And these two-digit numbers all have as first number a 1, which requires considerably less space for representation than the number 2. The hour numbers 20 to 24 beginning with the number 2 and taking up especially much space are not required.
In addition to the completely new optical appearance on the watch dial, the use of two hour display windows provides for an advantage in reading the hour numbers. If one single hour display window and one single hour disc were used, the hour disc would have to accommodate, in addition to nine one-digit numbers, fifteen two-digit numbers. The one-digit, and thus better readable, hour numbers are unfortunately during the hours of the night, i.e. a period in which one is usually asleep. As of 10 o'clock in the morning, the double-digit numbers begin, ending at midnight only. A display device for watches according to the invention, comprising two hour display windows and two hour discs, has a total of six double numbers during 24 hours only, which may be reduced further to only four double-digit hour numbers, namely two times 11 and two times 12, if the number 10 is indicated as Roman numeral X.
Preferably, the alternation between hour display using the day hours disc and hour display using the night hours disc take place at 8 o'clock a.m. and 8 o'clock p.m., but may also take place, for example, at 6 o'clock a.m. and 6 o'clock p.m.
The readability of the hour display is improved still further in an embodiment of the invention in which each one of the two hour discs is provided with a free portion having no hour numbers, with the free portion of the day hours disc being visible in the day hours display window during the hours of the night and the free portion of the night hours disc being visible in the night hours display window during the hours of the day.
The two hour discs may each be constituted by a circular disc, i.e. a circle covering the full area, or by an annular disc. It is also possible to form one of the two hour discs as a circular disc and the other hour disc as an annular disc.
In an embodiment of the invention, the hour discs have disc axes that are mutually spaced apart such that the hour discs do not overlap. In another embodiment of the invention, the hour discs have disc axes that are mutually spaced apart such that the hour discs are partly overlapping.
In an embodiment of the invention, the two hour discs are designed for geared drive, and for driving the two hour discs there is provided at least one driving device in the form of a driving gearwheel having thirteen teeth, twelve teeth thereof being provided for feeding, at hourly, intervals, the respective hour number of the respective hour disc, and the thirteenth tooth being provided for feeding the free portion of the respective hour disc to the visible range of the associated hour display window.
In an embodiment of the invention, there is arranged at least one minute display device and/or second display device externally of the two hour display windows.
In a particularly preferred embodiment of the invention, the display device for watches is in the form of a display module which is adapted to be drivingly coupled to a watch work. Such a display module is manufactured in the form of a separate constructional unit and is attached to the watch work or a gearing module of the watch provided with an inventive display device, which is driven by the watch work and attached thereto, while the driving device for the two hour display discs is drivingly coupled, for example, to a drive shaft or a drive pinion of the watch work or gearing module, respectively. The watch work may be a fully mechanical watch work or an electromotive watch work.
In an embodiment of the invention, the display module is designed such that the two hour display windows are at the 10 o'clock and 2 o'clock positions. By rotating the display module by 90°, the two hour display windows may also be arranged at the 7 o'clock and 11 o'clock positions. An off-center minute display may be provided for each of said hour display windows.
A display device according to the invention is suitable in particular for wristwatches and pocket watches.